Thermal and Metabolic Responses of Women With High Fat Versus Low Fat Body Composition During Exposure to 5 and 27°C for 120 Min

Glickman-Weiss EL, Nelson AG, Hearon CM, Prisby R, Caine N
Aviat Space Environ Med 1999; 70:284-8

Abstract

Background: Men with high fat body composition maintain higher core temperatures, and lower aerobic metabolic rates than their low fat counterparts thus, verifying the insulatory benefit of body fat. Females, on average have more body fat and less muscle mass than males, and may maintain rectal temperature (Tre) at a lower energy cost. Methods: The present investigation dichotomized female subjects by percent fat (low fat; n = 3, LF = 19.2 ± 3% vs. high fat; n = 4 HF: 29.9 ± 3%) to elucidate the thermal and metabolic responses during acute exposure to 5 and 27°C air for 120 min. An ANOVA was used to examine the following: Tre (°C), mean skin temperature (Tsk; °C), oxygen consumption (V(dot)O2; ml·kg-1·min-1) and tissue insulation (I; °C·m2·W-1). For Tre, a significant fat × time interaction (p < 0.05) was demonstrated at both 5 and 27°C, whereby Tre tended to be lower in the LF group than the HF group. V(dot)O2 at 5°C demonstrated a main effect for time only. For I, a main effect for time was noted at 5°C. Also for I, a trend (p = 0.06) toward a main effect of fat during exposure to 5°C was noted while at 27°C a main effect (p < 0.05) was demonstrated. Results: From this data it appears that under these conditions, the HF group demonstrated higher Tre and I values than their LF counterparts that was not accompanied with a differential response with respect to aerobic metabolic rate. Thus, the impact of body composition on energy expenditure to maintain Tre differs between LF and HF males and females.

Keywords: temperature regulation, gender differences, body composition.

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